Attributing ancient coins is a fun part of collecting coins. Roman
Imperial Coins are the easiest to attribute, whil Greek coins can be the
hardest.

Roman Imperial/Imperatorial/Republic

Fairly straight forward to attribute if you search an online
database or have the proper books

Byzantine (Romaion)

A little bit harder to attribute than Roman Imperial because there
is less resource material and the coins can often be hard to read.

Greek/Roman Provincial

A lot more difficult than Roman Imperial coins to attribute because
most of the inscriptions are in Greek and there is a lot less resource material
available.

Non-Classical (Celtic, Judean, Parthian, etc...)

Non Clasical coins can be as easy to attribute as Roman Imperial
coins or harder to attribute than Greek coins. It all depends on when and where
the coin came from and how much resource material there is to reference on that
culture.

Greek

Usually the hardest type of coin to attribute for the beginner. Not
only are there very few identifying inscriptions, the inscriptions are in the
Greek alphabet.

Favorite resources for attributing ancient coins:

ACA - User friendly discussion group devoted to the attribution of coins and the teaching of these skills to new collectors.

Wildwinds - One of the best
sites for "do it yourself" coin attribution

CoinsCatalog - Very nice
search engine with many ways to research coins

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